Phase transformations in novel hot-deformed Al–Zn–Mg–Cu–Si–Mn–Fe(–Sc–Zr) alloys

Role of Small Addition of Sc and Zr in Clustering and Precipitation Phenomena Induced in AA7075

“…The category of transformation line is changed with the content and composition of a particular element; the (non-)isothermal series of annealing steps are usually used [6,8,10,[17][18][19][20][21][22][23]. Despite having some disagreements and obscurity about the arrangement and the types of the hardening phases in the alloys, the decomposition of supersaturated solid solution is in the consistency with two precipitation sequences, where η′(MgZn2)phase (hexagonal)/η(MgZn2)-phase (hexagonal) and T′(Al2Zn3Mg3)-phase (hexagonal)/T(Al2Zn3Mg3)-phase (cubic) occur [15,19,20]. The precipitation of the semi-coherent η′-and T′-phases usually cause the age-hardening of the materials in contrast to the incoherent η-and T-phases [19,20,[22][23][24][25][26][27].…”

“…Despite having some disagreements and obscurity about the arrangement and the types of the hardening phases in the alloys, the decomposition of supersaturated solid solution is in the consistency with two precipitation sequences, where η′(MgZn2)phase (hexagonal)/η(MgZn2)-phase (hexagonal) and T′(Al2Zn3Mg3)-phase (hexagonal)/T(Al2Zn3Mg3)-phase (cubic) occur [15,19,20]. The precipitation of the semi-coherent η′-and T′-phases usually cause the age-hardening of the materials in contrast to the incoherent η-and T-phases [19,20,[22][23][24][25][26][27]. Many authors use different designations for the early precipitation phases formed during the precipitation; (co-)clusters/Guinier-Preston (GP) zones of different types usually appear during ageing at temperatures lower than ~150 °C [19,20,25,[28][29][30][31][32][33].…”

“…It enhances the usage of these alloys up to ~400 °C. The addition of Sc (0.05-0.20 at.%) and Zr (0.05-0.50 at.%) is the most effective Sc-Zr combination in aluminum due to the precipitation of the secondary spherical (coherent) core-shell ternary L12-structured Sc,Zr-containing phase [1,12,13,20,34,36]. The Sc and Zr content can help to refine and to affect the microstructure and the recrystallization temperature and therefore the materials in a non-recrystallized state improve their mechanical properties and resistance to corrosion [1,15,[40][41][42].…”

“…The Sc and Zr content can help to refine and to affect the microstructure and the recrystallization temperature and therefore the materials in a non-recrystallized state improve their mechanical properties and resistance to corrosion [1,15,[40][41][42]. It has recently been found in the commercial Al alloys with low Sc-Zr addition that the inter-metallic particles of primary Al3(Sc,Zr) phase have a multi-layered structure with many different shapes (dimension about 1-3 µm) and they appear inside (in the center of) the grains in principle [15,20].…”

“…This work is based on ongoing research, which has partially been recently published in References. [15,19,20,25]. The results of positron annihilation, microhardness and resistivity measurements during the isochronal annealing and subsequent natural ageing, thermal response and corrosion behavior were suitably supplemented with the powder X-ray diffraction and microstructure observations by scanning and transmission electron and atomic force microscopy.…”